AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Scale-Dependent Compensational Stacking of Deepwater Deposits: Carboniferous Ross Sandstone
(1) Department of Earth & Environmental Sciences, Tulane University, New Orleans, LA.
(2) Geology and Geological Eng., Colorado School of Mines, Golden, CO.
Compensational stacking, the tendency for sediment transport systems to preferentially fill topographic lows through deposition, is a concept widely used in the interpretation of the stratigraphic record. Recently a metric was developed to quantify the strength of compensation in sedimentary basins by comparing observed stacking patterns to what would be expected from simple, uncorrelated stacking. This method uses the rate of decay of spatial variability in sedimentation between picked depositional horizons with increasing vertical stratigraphic averaging distance. Initial exploration of this metric utilized reduced scale physical models and stratigraphy imaged in 3D seismic data. In this work we utilize the compensation index to describe the architecture of stratigraphy exposed in outcrops. The field sites analyzed are from the Carboniferous Ross Sandstone and include 1) Submarine lobe deposits exposed at Kilbaha Bay and 2) Submarine channel deposits exposed at Rinevella Point. In both data sets the architecture of stratigraphic packages is classified within a hierarchical framework of beds, stories, and elements. At both sites we measure an increase in the strength of compensation with an increase in scale (length or time) of interest. As a result, elements are more compensational then stories, which are more compensational than beds. Further, we note that submarine lobe deposits are more compensational than channelized deposits in the Ross Sandstone. Results from this analysis are compared to physical and numerical models which document that the handoff from random to ordered (compensational) stratigraphic packaging is related to the scale of autogenic processes in sedimentary basins.